The London Underground mosquito (Culex molestus) is a species of mosquito in the genus Culex found in the London Underground. It is thought to have evolved from the overground species Culex pipiens in the last few decades.

The evidence for this mosquito being a different species from Culex pipiens comes from research by Kate Byne and Richard Nichols. The two species have very different behaviours,[1] are extremely difficult to mate,[2] and show genetic drift.[3]

Biologists named the London Underground mosquito Culex molestus due to the way it assaulted Londoners sleeping in the Underground during the Blitz, although this name seems to already have been given to a species of mosquito found in Australia, named as long ago as 1775.[4]